The present invention relates to a method for manufacturing a nozzle for an ink jet head.
Conventionally, in an ink jet head of the "drop-on-demand" type, the ink is discharged in droplet form from a nozzle by reducing the volume of an ink flow path using piezoelectric ceramics. The ink is replenished by increasing the volume of the ink flow path, and is introduced into the ink flow path via an ink introduction opening. Characters or images are formed on a recording sheet by discharging the ink droplet from a group of nozzles according to predetermined printing data.
The properties and quality of the nozzles greatly influence the ink discharge characteristics of the ink jet head, and the manufacturing procedure of the nozzles therefore affects the end printing quality.
Known methods for manufacturing nozzles for an ink jet head, for instance, are known from: U.S. Pat. No. 4,508,749, wherein ultraviolet (UV) rays are projected onto a polyimide body; and Japanese Patent Publication Hei 2-42354 (corresponding to U.S. Pat. Nos. 4,728,392, 4,801,954, and 4,801,955) wherein photosensitive glass is etched. Further known is a method wherein nozzles are formed by injection molding, and deburring of flash and burrs formed around the nozzles is carried out using a laser. As the number of nozzle holes to be formed in a head may be as high as 32 or 64, the UV method is too time consuming and expensive for mass production. The etching procedure requires masking of both surfaces of the photosensitive glass to form a nozzle, and is also time-consuming and expensive. Lastly, laser deburring of injection molded nozzles is too slow when each nozzle is processed individually, and too expensive and the power consumption too high when several lasers are provided for parallel deburring of the nozzles.
Furthermore, conventionally, if the meniscus formed in each nozzle becomes withdrawn, the amount of ink expelled varies, and a stable ink discharge cannot be performed. To keep the ink discharge of the ink jet head uniform, maintaining a repeatable meniscus in each of the nozzles becomes very important.
Conventionally, an ink affinity processing step is separately applied to the inner wall of the nozzle plate, and the peripheral portions of the nozzles on the nozzle entry side. For example, a thin film having an ink affinity is applied to the nozzle entry side. However, since the ink affinity processing step is a separate process from the nozzle plate manufacturing step, the number of steps is high, special machinery is required and the conventional processing for ink affinity is therefore expensive, and less suitable for mass production.